Amplitude difference and similar time course of impulse responses in positive- and negative-contrast detection

Temporal impulse response functions (IRFs) were measured to investigate the temporal characteristics of positive- and negative-contrast detection in human vision. The IRFs were estimated using models from sequential double-pulse thresholds measured by the psi method. The results indicated that thresholds for positive contrast detection were significantly higher than those for negative contrast detection. However, positive- and negative-contrast IRFs were similar except for the first peak amplitude, reflecting the difference in sensitivity that originates from the summation operation rather than the linear filtering of the visual system.

► Temporal impulse responses of positive- and negative-contrast were measured. ► Stimuli had a circular wave-like shape under various spatial structures. ► Thresholds of positive-contrast were significantly higher than negative-contrast. ► Impulse response functions were similar except the first peak amplitude. ► The difference should originate from the summation (not the linear filter) process.